1. Field of the Invention
The present invention relates to the use of coherent energy pulses, as from high power pulsed lasers, in the shock processing of solid materials, and, more particularly, to methods and for improving properties of hollow core gas turbine engine blades by providing shock waves therein where the laser beam impacts the engine blade when the hollow core is filled with a substance or member. The invention is especially useful for enhancing or creating desired physical properties such as hardness, strength, and fatigue strength.
2. Description of the Related Art
Known methods for shock processing of solid materials, particularly laser shock processing solid materials, typically use coherent energy as from a laser oriented perpendicular to the workpiece.
Laser shock processing techniques and equipment can be found in the U.S. Pat. No. 5,131,957 to Epstein.
Known laser shock processing systems tend to form a relatively small, in cross sectional area, laser beam impacting on the surface of the workpiece. This has been accomplished, since to sufficiently work a surface of the workpiece, sufficient laser energy must be applied over a particular area. The smaller the area with the same amount of energy leads to a greater energy per unit area application. The more energy per unit area applied, the deeper the residual compressive stresses are applied to the workpiece.
In a number of gas turbine engine blades, particularly those in the high temperature sections of the gas turbine engine, there are hollow core blades that include air intakes in the blade attachment, or root, connected into a hollow space within the blade airfoil portion.
During two-sided split beam laser peening operations the airfoil section would collapse for some types of gas turbine blade geometries, particularly geometries where there is a thin cross section with a hollow space disposed therein.